Check if current Command Prompt was launched as the Administrator

Found this on Stack Overflow:

@echo off
goto check_Permissions

:check_Permissions
echo Administrative permissions required. Detecting permissions...

net session >nul 2>&1
if %errorLevel% == 0 (
    echo Success: Administrative permissions confirmed.
) else (
    echo Failure: Current permissions inadequate.
)

pause >nul

This checks for high integrity level. (works for Windows Vista and higher)

@echo off

whoami /groups | find "S-1-16-12288" > nul

if %errorlevel% == 0 (
 echo Welcome, Admin
) else (
 echo Get lost, User
)

Many, many answers to this and multiple other questions across SE (1,2,3 to name a few), all of which are deficient in this way or another, have clearly shown that Windows doesn't provide a reliable built-in utility. So, it's time to roll out your own.

Without any further dirty hacks:

Compile the following program (instructions follow), or get a precompiled copy. This only needs to be done once, then you can copy the .exe everywhere (e.g. alongside the Sysinternals Suite).

The code works in Win2k+¹, both with and without UAC, domain, transitive groups, whatever - because it uses the same way as the system itself when it's checking permissions. chkadmin prints "Admin" or "Non-admin" and sets the exit code to 0 or 1, respectively. The output can be suppressed with the /q switch.

chkadmin.c:

#include <malloc.h>
#include <stdio.h>
#include <windows.h>
#pragma comment (lib,"Advapi32.lib")

int main(int argc, char** argv) {
    BOOL quiet = FALSE;
    DWORD cbSid = SECURITY_MAX_SID_SIZE;
    PSID pSid = _alloca(cbSid);
    BOOL isAdmin;

    if (argc > 1) {
        if (!strcmp(argv[1],"/q")) quiet=TRUE;
        else if (!strcmp(argv[1],"/?")) {fprintf(stderr,"Usage: %s [/q]\n",argv[0]);return 0;}
    }

    if (!CreateWellKnownSid(WinBuiltinAdministratorsSid,NULL,pSid,&cbSid)) {
        fprintf(stderr,"CreateWellKnownSid: error %d\n",GetLastError());exit(-1);}

    if (!CheckTokenMembership(NULL,pSid,&isAdmin)) {
        fprintf(stderr,"CheckTokenMembership: error %d\n",GetLastError());exit(-1);}

    if (!quiet) puts(isAdmin ? "Admin" : "Non-admin");
    return !isAdmin;
}

To compile, run in Windows SDK command prompt:

cl /Ox chkadmin.c

(if using VS2012+, more adjustments are needed if you need to target 2k/XP)

---

_{The method is courtesy of https://stackoverflow.com/questions/4230602/detect-if-program-is-running-with-full-administrator-rights/4230908#4230908}

¹_{MSDN claims the APIs are XP+ but this is false. CheckTokenMembership is 2k+ and the other one is even older.}